It is well known to use interferometric holography in non-destructive testing. It is also known to develop a photographic film used in such testing in situ in order to expedite the testing procedure. Reference may be had to U.S. Pat. No. 3,739,702 which is incorporated herein by reference. This patent discloses water in the developing chamber during the imaging of the film. The in situ development of film in apparatus for exposing and developing film and projecting the image of the developed film is disclosed in U.S. Pat. No. 3,200,724 which is incorporated herein by reference. In this patent water is used in the developing chamber to improve the transmission of light through the film holding device and to eliminate the drying of the film after development and prior to protection.